Fighters' weapons "may not be powerful enough" to
penetrate the shields of the droid control ship, a very large automated
battleship.
This suggests that fighters possess firepower that presents a marginal
threat to capital ships.
We see theater and large-individual sized shields deployed by the
droids and Gungans. All sizes appear to very adequately stop blaster
fire, but a determined creature or droid may push through at low
velocity.